Plastic (for example, polyethylene) modified asphalt can significantly improve the rutting resistance and high-temperature resistance of an asphalt pavement, while a crumb rubber modified asphalt can greatly improve the cracking resistance of the asphalt pavement. An alloy prepared by combining the plastic-modified asphalt and the crumb rubber modified asphalt can improve the rutting resistance and the cracking resistance of the pavements. At present, the plastic and the crumb rubber are substantially applied to an asphalt pavement by wet and dry methods. The wet method comprises mixing the plastic and the crumb rubber with the warm asphalt at high temperature to provide a rubber-plastic modified asphalt, which is then mixed with an aggregate. The dry method comprises mixing the plastic or the crumb rubber as a modifier with other stone material in a mixing pot to prepare a mixture.
In the process of the wet method, the rubber-plastic material can be sufficiently reacted with the asphalt at high temperature to become a part of the asphalt cementing material and increase the viscosity of the asphalt matrix, which can then serve as a binder in the mixture. However, the wet method suffers from the disadvantages of complicated process, time consuming, high energy consumption, high smoke pollution and expensive cost and equipments, as well as strictly controlled shearing and agitating time so as to avoid excessive degradation. In the modified asphalt obtained by a wet method, the viscosity of the matrix asphalt and the asphalt/stone ratio in the mixture will be correspondingly increased. Furthermore, for the purpose of obtaining a rubber-plastic modified asphalt having stable performance, the type of the crumb rubber should be selected, for example, a crumb rubber from a jumbo tyre containing high amount of natural rubber (comprising more than 60% of the rubber used a tyre) are usually used. This hinders the development of the wet method, and in turn the application thereof. Existing dry methods have the advantages of low pollution and easy application, however, the mixture prepared by the same cannot increase the viscosity of the asphalt matrix, and thus can not significantly improve the rutting, high temperature and cracking resistance of the pavements.
A warm mix asphalt (about 140° C.) has the advantages of being able to be processed and spreaded at a temperature lower than conventional hot mix asphalt (about 170° C.), and thus arouse wide attention by greatly reduce energy consumption and pollution.
A warm mixing method is urgently needed for solving the problem caused by the high temperature for processing a rubber-plastic asphalt, so that the defects of complicated process, time consuming, high energy consumption, and high smoke pollution existing in the wet process of the prior art can be overcome, and the temperature for hot mixing the asphalt can be reduced, while combining the modifying effect of a wet method and the advantages of low pollution and easy application of a dry method. Therefore, there is an urgent need for a rubber-plastic alloy having high fluidity.